TODAY, ON WORLD OCEANS DAY, a tiny turtle will pop its head out of the sand and amble a trail towards the sea. Slowly, the beach will be transformed into 150 trails, heading towards the setting sun. Some of these turtles will return to that very beach over their lifetime for nesting. Many, however will not.
Beyond the natural mortality rates associated with turtles, the future of new hatchlings is increasingly uncertain on account of the effects of a host of challenges, including anthropogenic (man-made) climate change.
The link between turtles and climate change: Sea turtles’ sex is determined by the incubation temperature of turtle eggs. Each species has a temperature threshold where an equal distribution of male and female hatchlings will occur, but when the environment warms above this pivotal temperature, females will be produced.
A recent study published in the Journal of Experimental Marine Biology and Ecology by Laloë, Esteban et al. drew potentially alarming conclusions. The study based its analysis on sand temperature measurements and historical and current environmental data, and projected the entire feminization of the three sea turtle populations in St. Eustatius due to increased air temperatures within the next century.
The effect of feminization on the population is not necessarily conclusive of local sea turtle extinction, though it represents a very real possibility. The study noted that turtles are polygynandrous; that is, a male will mate with more than one female during breeding season, and females have the capacity to store sperm for future fertilization of clutches of eggs. These adaptations may render the turtles resilient to these changes.
Yet, despite these adaptations, the study suggests that these endangered species may not be viable in the face of an “an extremely male-depleted population.” Moreover, feminization is but one risk posed by the increased temperatures. Previous studies have shown that the warming temperatures may affect the mortality rates of hatchlings; a phenomenon which is poorly understood at this time.
The projections of the study predict that as little as 2.4% of green turtle hatchlings will be males by 2030, and falling further to 0.9% of the population by 2090. In the absence of evolutionary adaptive changes in nesting habits by the turtle, the only management strategies which may be of some assistance require scaling up interventions targeting marine turtle protection.
Strategies such as artificially lowering incubation temperatures through the shading of nests, or relocating turtle clutches to deeper depths may be the only resources available to the Caribbean to avoid the localized extinction of turtles in the region.
A future without turtles? The ecological, social, and economic benefits of rich biodiversity, including marine turtles, cannot be overstated. The risk associated with climate change for turtles are only compounded by the poaching of eggs, the impact of the increased presence of sargassum seaweed and the destruction of habitats with the ever-increasing development of beachfronts throughout the region, and the certain risks which those developments pose to turtles’ nesting habits.
Mitigating climate change, and ensuring effective adaption measures to protect marine life, are acutely necessary for the Caribbean region, lest the region sees a future without turtles.